This invention relates to the synthesis and use of chiral ionic liquids based on a substituted pentose, furanose, hexose, or pyranose sugar. The compounds and processes to make or use them are provided.
Ionic liquids have been the subject of much recent research. The surge in interest in ionic liquids has been due chiefly to their potential to replace volatile organic compounds as the solvent in laboratory and industrial applications (Pandey, Anal. Chim. Acta, 556:38-45, 2006). Hazardous chemicals are characterized by their volatility because they are easily evaporated from a reaction mixture or reactor, and then inhaled by workers. In contrast, ionic liquids do not evaporate under conditions typical for chemical reactions, separations, and analyses. Released into the environment, volatile organic compounds may also act directly as toxins or degrade into pollutants. In addition to their environmentally friendly nature, ionic liquids have been used in a variety of chemical applications including catalysis, chromatography, and spectrometry. As yet, the full scope of ionic liquids has not been investigated and much effort is being put into understanding the properties and behavior of this class of solvents (Welton, Chem. Rev., 99:2071-2083, 1999).
The unique environment provided by ionic liquids is thought to be a solution to many reactions which are unfavorable in conventional solvents. Chiral ionic liquids have renewed interest in using chiral solvents to control stereoselectivity (Baudequin et al., Tetrahedron: Asymmetry, 16:3921-3945, 2005). Unlike conventional chiral solvents, chiral ionic liquids are synthesized easily in good yields. Chiral ionic liquids may be based on amino acid, hydroxyl acid, amine, amino alcohol, terpene, and alkaloid compounds or they may be made by asymmetric synthesis. They may possess central, axial, or planar chirality; their chirality may arise from either the anion or cation of the salt. Here, we show that substituted sugars possessing a number of different chiral centers may be used to synthesize chiral ionic liquids.
Therefore, it is an objective of the invention to provide a novel class of chiral ionic liquids for use as solvents in chemical reactions, separations, and analyses. A long-felt need is addressed thereby. Further objectives and advantages of the invention are described below.